British school’s for French people (7)
I believe the answer is:
bretons
'french people' is the definition.
(people of Brittany in France)
'british school's' is the wordplay.
'british' becomes 'br'.
'school's' becomes 'etons' (famous UK public school).
'br'+'etons'='BRETONS'
'for' is the link.
(Other definitions for bretons that I've seen before include "Natives of St Malo" , "Natives of Brittany" , "Frenchmen" .)